1. Field of the Invention
This invention relates to dental pulp testers, and, more particularly, to a pulp tester for automatically producing an increasing intensity electrical stimulus upon contact of a dental probe with a tooth, and for displaying the intensity of the electrical stimulus at the time the probe is removed from the tooth.
2. Description of the Prior Art
When a tooth has been subject to decay, physical trauma, thermal changes or irritation by sweet foods or deep fillings, the pulp tissue becomes inflamed. When this inflammation is left untreated for a long time, the ensuing pulpal inflammation generally proceeds to a severe infection with abscess formation about the root tips. It is at this stage that many teeth require extraction and that endodontic procedures, designed to help remove this infection, are least successful.
Electric devices used to test the vitality of pulpal tissue have long been used as diagnostic aids by dentists. For example, these devices have found application where a patient complains of pain on one side of the mouth and cannot isolate the specific tooth from which the pain emanates. Also they have been used in the diagnosis of decay which develops around the borders of fillings in teeth with existing restorations--a situation where x-rays alone may not indicate the presence or extent of the decay.
In actual operation, a stimulating electrode of an electric pulp tester is applied to a tooth which is undergoing examination. The operator then gradually raises the level of the voltage at the electrode until the patient feels a tingling or mild electric shock in the tooth that is being touched by the electrode. By comparing the voltage level to which the patient responds with the level at which other of his normal teeth respond, the dentist can make a diagnosis on the state of inflammation or vitality of the dental pulp in the tooth under examination.
While the existing dental pulp testers have proved to be valuable diagnostic tools, they suffer from certain disadvantages which have limited their utility. The principal disadvantage of such testers has been the speed at which they can be used. Conventional pulp testers produce an electrical stimulus which it is manually switched to an on condition, and which is subsequently manually increased. Consequently, it is necessary for a dentist to divert his attention from the patient to the pulp tester in order to increase the intensity of the stimulation. Some conventional pulp testers have attempted to minimize this problem by placing the intensity control on the probe itself, but it is still necessary for the dental practitioner to direct his attention away from the patient to this control. An additional factor in decreasing the speed at which conventional pulp testers may be used is the difficulty in reading their display devices. Generally, these displays are rotary or sliding controls which require the practitioner to interpret the position of the control dial with respect to a fixed mark, and then record the stimulus reading corresponding to the position of the control dial. Although approximate readings can be obtained fairly rapidly, it is very difficult to accurately interpret such displays at a fairly rapid rate.
Another disadvantage of conventional pulp testers is that a reasonable testing rate can only be achieved by rapidly increasing the intensity of the stimulation. However, this rapid increase causes the intensity to "overshoot" the point where the patient can perceive the stimulation before the probe can be removed from the tooth and the increase in intensity can be terminated. Consequently, the patient is subjected to unnecessary pain, and the intensity readings taken from the display are erroneously high.
Still another disadvantage of conventional pulp testers is the characteristics of the electrical stimulus which they apply to a tooth. The electrical stimulus is generally either a continuous voltage having a magnitude which increases with time, or a continuous series of pulses having an amplitude which increases with time. As the dental pulp is stimulated the tooth loses some of its sensitivity until the stimulus is removed and the pulp nerves are "reset". Since these conventional stimulus forms do not allow the pulp to become reset during a test, the level of stimulus required for the patient to perceive the stimulus is unduly high.
In summary, conventional pulp testers are inherently inaccurate, and they are incapable of being used at a relatively fast rate.